106 Bev. H. B. Haweis [Feb. 7, 



faction. When the pulses succeed each other with a certain degree 

 of rapidity, a musical sound is generated. The scientific instrument 

 known as the " syren " illustrates this. A musical sound varies in 

 three ways — in loudness, pitch, and quality. The loudness depends 

 on the extent of the vibrations, the pitch on the rapidity of the 

 vibrations, and the quality on the mode of vibration. The tuning- 

 fork demonstrates to the eye the extent and rapidity of these aerial 

 vibrations; the pianoforte and violin will enable us to analyze the 

 quality, which depends on the mode of vibration. 



It is obvious that the same note struck on violin, pianoforte, 

 flute, &c., differs in timbre, or quality. What causes that difference ? 

 Helmholtz has shown us that most musical notes are not simple, but 

 composite, sounds. He calls these clangs ; they contain within them 

 certain buried notes, belonging to a fixed series, and these he calls 

 overtones ; and the quality of every clang * depends upon the number, 

 order, and intensity of these overtones. The presence of overtones in 

 a clang can be easily demonstrated by striking a note on the piano- 

 forte, just releasing the damper of its octave, and by the law of 

 resonance the overtones, often up to the eighth, will be heard re- 

 sounding sympathetically, which would not be the case were they not 

 really buried in the clang of the one struck. 



Overtones. 



^^- 



m 



22: 



The law obeyed by the overtone series can be seen at a glance, 

 and it is to the presence, number, order, and relative intensity of 

 these overtones that we owe all that variety of musical timbre which 

 makes the charm of an orchestra and furnishes with inexhaustible 

 tonal resources the empire of musical sound. 



An approximately pure tone like that of a tuning-fork, or the 

 upper notes of a piano, is insipid and characterless. Eichness and 

 character come in with the presence of these latent overtones, the 

 order of which the diagram will show you at a glance. All are not 

 always present, nor are those present always in the same place of the 

 series, nor are they always of equal intensity ; therefore it is said that 

 quality depends on the number, order, and relative intensity of the 

 overtones present in a clang or composite note. Now as long as we 

 have but one clang, yielding to the ear but one definite musical note, 

 the construction of a scale on violin or piano with such clangs is 

 simple. But when you come to bells, I believe you have to deal in 



♦ Composite note. 



